A full Moon close to ‘perigee’ – known informally as a ‘supermoon’ – will be visible at 03:35 BST in the early hours of 8 April 2020. This should allow for a stunning sight as the Moon will appear full and bright: relatively larger and brighter than normal. But you don’t strictly need to wait until then to admire this lunar spectacle.
From the UK, the Moon will rise on the evening of 7 April from around 19:06 BST and will be seen high in the sky from 21:00 BST onwards.
But what is meant by ‘perigee’ and ‘apogee’ Moons?
The lunar orbit is not a perfect circle, but is elliptical, meaning the Moon’s physical distance from Earth is constantly changing.
The two orbital extremes are known as perigee (closest to Earth) and apogee (farthest from Earth) and each occurs once a month.
The visual impact of a perigee full Moon compared to an apogee full Moon is that the full Moon appears approximately 30% brighter and 14% larger.
Because previous and subsequent full Moons to the perigee full Moon have been near to perigee themselves, the difference from one month to the next is not dramatically noticeable, but a bright full Moon is always a great reason to get out and look up at the night sky.
You could use a stargazing reference guide or download a smartphone astronomy app and teach yourself the constellations at the same time (although you should expect that bright full Moon to overshadow what else is on show to a certain extent).
Read more about observing the Moon:
- Patrick Moore’s guide to observing the Moon
- Why does the Moon’s appearance change?
- How to observe the Moon
The timing of full Moon and lunar perigee or apogee are not in sync but drift in and out of phase over the course of many lunar orbits.
During certain months, full Moon occurs closer to perigee than others. Once one occurs, the next two will typically be close to perigee too.
- This month’s full Moon occurs on 8 April at 03:36 BST with perigee on 7 April at 18:10 UT
- The first of 2020’s ‘supermoons’ occurred on 9 February. On this occasion full Moon was at 07:34 UT, with lunar perigee on 10 February at 20:32 UT.
- The next full Moon occurred on 9 March at 17:48 UT, with perigee on 10 March at 06:34 UT.
Pete Lawrence is an experienced astronomer and co-host of The Sky at Night. This article originally appeared in the February 2020 issue of BBC Sky at Night Magazine.